The invention disclosed herein pertains to a machine for stacking articles. In particular, the invention resides in an improved device for stripping a stack of articles from the stacking machine so the stack can be forwarded to a packaging machine, for example. The new stripping device is especially efficacious in stripping stacks of pliant or supple articles such as sanitary pads and pads having almost gossamer delicacy which are inclined to bunch up and deform when they are handled.
The new stripper solves the problem of stack instability and deformation that occurs in conventional stackers when a stack is being stripped from the stacker machine to where the stack can be conveyed to the next work station, such as to a packaging machine. The new stripper will be demonstrated in connection with stacking feminine sanitary pads.
A widely used conventional stacker has parallel conveyor chains usually running on sets of three pairs of sprockets whose horizontal rotational axes are parallel and arranged at the corners of a triangle. A series of rows of paddles or fingers are fastened to the conveyor chains and the paddles extend outwardly from the chains. At one place, where the paddle carrying chains pass over a sprocket, the paddles fan out to provide space between them for feeding pads from a flat belt conveyor into the space between consecutive paddles. This is usually done adjacent a sprocket at one of the lower corners of the triangle. Paddles then carry the pads upwardly and when the conveyor chains turn around the uppermost sprockets, the articles transfer from a trailing paddle in a pair to a leading paddle so the pads invert as they begin to descend. After that, the paddles, which are now descending with the conveyor chains, extend out horizontally away from the chains, one above the other, so that a pad on each of the paddle groups contribute to forming a stack of pads or other articles which are resting on the paddles and are spaced apart vertically by the distance between each two consecutive sets of paddles. The paddles are comprised of individual paddle elements or fingers which are laterally spaced from each other. In prior art apparatus, the lowermost pad in an accumulated stack is settled on the upper surface of a platform in a stripper device. The platform has slots to allow the conveyed paddles or fingers to pass downwardly through the platform and to continue circulation on the conveyor chain loop after the lowermost pad has been left behind on the slotted platform. Stripper bars extend vertically adjacent the pads while the pads are still on the paddles. The vertical length of the stripper bars is equal to the sum of the distances between the horizontally extending paddles on each of which is a pad that will be stripped from the paddles to form a stack. The horizontal platform and vertical stripper bars are shifted laterally when a stack containing a predetermined number of articles has accumulated. The stripper bars move between the laterally spaced apart fingers of the paddles at each level so the bars push the pads in unison to one side so as to strip them off of the paddles. The stack is pushed beyond the outer tips of the paddles onto a shuttle table in line with a shuttle that executes reciprocal motion to push the stack from the table to which it was transferred to a conveyor belt which feeds the stacks to a packaging machine, for example.
In the conventional stacker just outlined, the lowermost pad in the stack is deposited on the slotted platform underneath and in vertical alignment with all of the pads still resting on the paddles above it. The top of the platform is at the same level as the top of the shuttle table so the lowermost pad is dragged along the plane surface by the stripper bars. When all of the pads are pushed clear of the outer tips of the fingers of the vertically spaced apart horizontally extending paddles, every pad in the stack falls vertically through a distance equal to its elevation in the stack minus the sum of the thicknesses of the pads beneath it. The result in conventional strippers is that the articles in a stack are sometimes vertically misaligned and out of balance which has caused problems at the input of the packaging machine. Misalignment results to a large extent from the lowermost pad being dragged along the surface of the stripper platform and the shuttle table which also causes undesirable deformation and scuffing of the pads or other delicate articles which are undergoing stacking.